Coronaviruses are named for the crown-like spikes on their surface. There are four main sub-groupings of coronaviruses, known as alpha, beta, gamma, and delta. Human coronaviruses were first identified in the mid-1960s. There are 7 coronaviruses known to infect humans. Of those, only MERS-CoV and SARS-CoV are routinely capable of causing severe disease. The rest are responsible for mild respiratory illnesses like the common cold but can cause severe infections in immunocompromised individuals. The clinical severity of the 2019-nCoV is unknown at this time, although fatal cases have occurred.
Human Coronavirus Types
The seven coronaviruses that can infect people are:
- Common human coronaviruses
- 229E (alpha coronavirus)
- NL63 (alpha coronavirus)
- OC43 (beta coronavirus)
- HKU1 (beta coronavirus)
- Other human coronaviruses
- MERS-CoV (the beta coronavirus that causes Middle East Respiratory Syndrome, or MERS)
- SARS-CoV (the beta coronavirus that causes severe acute respiratory syndrome, or SARS)
- 2019 Novel Coronavirus (2019-nCoV)
People around the world commonly get infected with human coronaviruses 229E, NL63, OC43, and HKU1. Sometimes coronaviruses that infect animals can evolve and make people sick and become a new human coronavirus. Three recent examples of this are 2019-nCoV, SARS-CoV, and MERS-CoV:
SARS-CoV
The only recognized SARS-CoV outbreak began in China in 2002 and spread internationally, most notably to Toronto, Canada. From November 2002 to July 2003, the World Health
Organization (WHO) reported 8,437 SARS cases and 813 deaths. Like other coronaviruses, SARS-CoV is transmitted from person to person through respiratory droplets and close contact.
The incubation period is 4 days (range 1 to 13 days). The main symptoms of SARS are fever, headache, and discomfort. The case fatality risk is approximately 10%.
MERS-CoV
MERS-CoV was first identified in Saudi Arabia in 2012. To date, there have been more than 2,400 cases, mostly in the Middle East. Individual cases and small clusters continue to be reported
in that region. Travel-related MERS cases have also been reported in South Korea, where it caused a significant hospital-based outbreak in 2015, and in the United States, where 2 very mild
cases were diagnosed. MERS-CoV is transmitted from person to person via respiratory droplets and close contact.
The incubation period is 5 days (range 2 to 15 days). The main symptoms of MERS are fever, chills, generalized myalgia, cough, shortness of breath, nausea, vomiting, and diarrhea. The case fatality risk is approximately 35%.
2019-nCov
A mysterious pneumonia outbreak first reported December in Wuhan, central China’s Hubei Province, has quickly spread across the country and around the world. Scientists have attributed the outbreak to “2019-nCoV,” a new strain of coronaviruses that has not been previously identified in humans.
What makes it different?
Coronaviruses are zoonotic, meaning they are transmitted from animals to humans. SARS-CoV, for instance, was transmitted from civet cats to humans while MERS-CoV travelled from dromedary camel to humans. But in both cases bats are the original host. Civet cats and cats serve as an important intermediary that carries virus from the winged mammal to humans.
The 2019-nCoV may also originate in bats, a team led by renowned Chinese virologist Shi Zhengli said earlier, while the intermediary host remains unknown. Their route of transmission and symptoms seem to have much in common, whereas the novel coronavirus is spreading far more quickly than the other two diseases.
The WHO Director-General, Dr Tedros Adhanom Ghebreyesus, declared the novel coronavirus (2019-nCoV) outbreak a public health emergency of international concern (PHEIC) on 30 January 2020. This is the 6th time WHO has declared a PHEIC since the International Health Regulations (IHR) came into force in 2005. Before the new coronavirus declared a global emergency by the WHO, there have been five global health emergencies since such declaration was formalized: swine flu (2009), polio (2014), Ebola (2014 then again in 2019), and Zika (2016). Compared with these diseases, WHO’s preliminary estimate shows the novel coronavirus has a relatively low level of mortality rate and contagiousness for now.
“The main reason for this declaration is not what is happening in China but what is happening in other countries,” WHO Director-General Tedros Adhanom Ghebreyesus explained.
The major concern is the threat to countries with fragile health systems. “In many ways, China is actually setting a new standard for outbreak response,” which deserves “respect and appreciation, and are worth learning,” Ghebreyesus said. After the outbreak, the Chinese government is responding swiftly with strong measures.
Within days of the first cases being reported, Chinese scientists identified the genome sequence of the new coronavirus and shared it with the world. In an unprecedented move, the epicenter of the outbreak Wuhan was locked down to curb the spread of the virus. Doctors, nurses, funds and medical materials poured into the city for help.
China has also vowed to build several makeshift hospitals in days to treat patients infected with the novel coronavirus. The first such hospital, Huoshenshan Hospital in Wuhan, was formally delivered to military medics – less than 10 days after the construction began.
China has insisted timely and regular release of epidemic information. In other moves, the country extended the Spring Festival holiday and the closure of businesses, and postponed the opening of the new school semesters. The 31 provincial-level regions all activated top-level emergency responses to the coronavirus.
China is confident in and capable of effectively containing the novel coronavirus epidemic, and eventually defeating it, the country’s National Health Commission said in a statement. The WHO chief echoed the view, saying he believes that China will effectively contain and eventually defeat the epidemic.
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